Harrisson’s Dogfish(Centrophorus harrissoni) was previously reported from Western Australia (Last and Stevens 1994) but that population is now known to be the Western Gulper Shark (C. westraliensis) (White et al. 2008, Last and Stevens 2009).

At the time of the previous IUCN Red List assessment for this species (in 2003), taxonomists recognized that the western form was distinct and required a new name, therefore Assessors treated C. harrissoni as only occurring of eastern Australia for that assessment (i.e., the current assessment refers to the same taxonomic concept as the one assessed in 2003).

Justification:
The first Red List assessment (2003) for Harrisson’s Dogfish (Centrophorus harrissoni) (Critically Endangered) was based on the documented >99% decline of the species on upper continental slope grounds off central and southern New South Wales (NSW) and eastern Victoria, inferred from the results of fishery-independent trawl surveys. This part of its range is still continually fished and there is no evidence that the numbers of Harrisson’s Dogfish have recovered on these trawl grounds. Its relatively narrow continental slope habitat (275–1,050 m depth range), probable late age at maturity and very low fecundity (maximum of one or two pups every two years) make Harrisson’s Dogfish extremely vulnerable to rapid population depletion by commercial fishing (particularly trawling) and also prevents any quick recovery after such depletion.

However, since the first assessment, the species is now known to occupy a greater geographical range than previously thought and a number of conservation measures have been implemented. While records from the Kermadec and Norfolk Ridges are based on few specimens, there is reportedly little fishing effort in this peripheral part of its range. A recent longline survey and other observations confirmed the presence of significant numbers of Harrisson’s Dogfish along the southern Queensland and northern NSW upper continental slope, as well as on a series of offshore seamounts (Tasmantid Seamounts) off eastern Australia. Throughout this part of its range (~50%), there is only small-scale commercial fishing (drop-line and powered handline) which is thought to have minimal impact on Harrisson’s Dogfish numbers.

Several conservation measures have also been introduced specifically to protect and enhance Harrisson’s Dogfish numbers. Earlier restrictive catch limits (to prevent target fishing) have been replaced by a total ban on retaining any Harrisson’s Dogfish for sale. The Gulper Shark protection areas off Sydney and eastern Bass Strait have been increased in size and closed to all methods of fishing, and there is a ban on trawling below 700 m along the east coast south from Sydney (designed to protect all deepwater sharks). New management rules for the Tasmantid Seamounts, specifically designed to protect Harrisson’s Dogfish, have been introduced. The Derwent Hunter Seamount is now closed to all fishing while fishing on the Britannia and Queensland Seamounts is restricted to handlines with powered reels. The Barcoo and Taupo Seamounts remain closed to trawling but open to line fishing. However, all seamount fishing is subject to 100% monitoring, and there will also be a vessel interaction limit of three Gulper Sharks and if reached, the seamount will be closed to that boat for 12 months.

Recently calculated depletion estimates for Harrison's Dogfish off eastern Australia indicated a 79% reduction in virgin population. Considering this estimate, and the species' sporadic distribution on lightly or unfished ridges and seamounts in the Tasmin and adjacent seas, Harrisson’s Dogfish is now assessed as Endangered, with an overall population decline inferred to be about 70%.

Harrisson’s Dogfish ranges continuously along the east coast of Australia from southern Queensland (26°40’S) to South East Cape, Tasmania (43°40’S), as well as on the Fraser Seamount off Queensland and Taupo Seamount off New South Wales (NSW) (Graham and Daley 2011). During 2011–2012, the presence of Harrisson’s Dogfishwas also confirmed on the Recorder, Britannia, Derwent Hunter and Barcoo Seamounts, establishing its presence on all of the Tasmantid seamounts except for Gascoyne Seamount, the most southern (K. Graham pers. obs.). In February 2012, a specimen caught close to Lord Howe Island was deposited in the Australian Museum, Sydney (Registration No. I.45944-001). Duffy (2007) gives details of single specimens from each of the Kermadec and Three Kings Ridges to the north of New Zealand, and reports nominal records from the northern Norfolk Ridge south of New Caledonia, the Three Kings Ridge and the Wanganella Bank just outside the New Zealand Exclusive Economic Zone (EEZ). Duffy (2007) further states: ‘Collections indicate C. harrissoni is probably continuously distributed along the Norfolk Ridge from 17°30’S to at least 33°S.’

Harrison's Dogfish was first recorded from FIS Endeavour survey catches during 1904-1914 (McCulloch 1915) but fishery impacts on the species' population did not begin until the 1970s when commercial trawling began on the NSW upper slope (Graham et al. 2001, Tilzey and Rowling 2001). Since then, gulper sharks, including Harrisson’s Dogfish, were commercially exploited off the east coast of Australia, but there has been no estimate of total population numbers.

In the northern half of its range off Australia’s east coast (southern Queensland to central New South Wales (NSW)), a small-scale line fishery targets teleosts along the upper slope and on offshore seamounts. A targeted Gulper Shark survey using auto-longlines on the upper slope between Brisbane and Tasmania in 2009 caught 105 Harrisson’s Dogfish off northern NSW with a mean catch rate of 3.3 dogfish per 1,000 hooks (Williams et al. 2012). On the same survey, 12 Harrisson’s Dogfish were caught at the Taupo Seamount (~200 nm off central NSW) at 4.0 dogfish per 1,000 hooks. In February 2011, auto-longlining over four days on the Britannia and Queensland Seamounts off southern Queensland caught 49 Harrisson’s Dogfish at 2.5 fish per 1,000 hooks (K. Graham pers. obs.). During 2011–12, the ‘Minor Line’ (handlines on mechanised reels) fishery that targets the teleost Hyperoglyphe antarctica on seamounts was scientifically monitored and 111 Harrisson’s Dogfish were recorded with an overall catch rate (across all seamounts) of 3.3 per 1,000 hooks; on Recorder and Britannia Seamounts, Harrisson’s Dogfish were targeted for tagging and catch rates as high as 40 per 1,000 hooks were achieved (K. Graham pers. obs.). The coastal drop-line fishery off northern NSW landed relatively small numbers of demersal sharks and the impact of this fishery on Harrisson’s Dogfish is considered low; in the seamount ‘Minor Line’ fishery, dogfishes are not retained and a high proportion of those captured are likely to survive if returned quickly to the sea.

In contrast, the relative abundance of the species in the southern half of its range between Newcastle (33°00’S) and Tasmania (44°00’S) has been severely impacted by commercial fishing. A fishery-independent trawl survey on the upper slope (200–650 m depth) off NSW between the Sydney area (33°30’S) and the Eden-Gabo Island area (38°20’S) in 1996–97 found a >99% decline in relative abundance of all Gulper Sharks (Centrophorus spp.) since the initial survey in 1976–77 (Andrew et al. 1997, Graham et al. 1997, 2001). Further south off eastern Bass Strait and Tasmania, trawling and targeted gillnet fishing in the 1980s and 1990s also severely depleted numbers (Daley et al. 2002). Although it is now illegal to retain Harrison's Dogfish for sale (AFMA 2012b), incidental fishing mortality by demersal trawlers and auto longliners targeting upper slope teleosts will continue to maintain pressure on the remnant population of Harrisson’s Dogfish off southeastern Australia.

The 2009 targeted longline survey for Gulper Sharks (see above) confirmed that numbers of Harrisson’s Dogfish remain low on regularly fished grounds between Sydney and Bass Strait (~0.4 dogfish per 1,000 hooks) and catches through this southern part of its range included no mature females. However, at three sites off Flinders Island that included areas closed to trawling (Daley et al. 2010), 85 Harrisson’s Dogfish were caught (6.3 dogfish per 1,000 hooks) suggesting that the protected areas were having a beneficial effect on population numbers.

In 2012, utilizing all available data, CSIRO (Commonwealth Scinetific and Industrial Organisation) scientists calculated depletion estimates and pre-fishery carrying capacity for Harrison's Dogfish in Australian waters (AFMA 2012a,b). The overall depletion estimate (proportion of the population remaining) was 21% (range 11-31%) with the estimate for the continental slope population 11% (4-20%) and seamount population 75% (50-100%).

With only two specimens known from New Zealand EEZ waters, and sporadic (nominal) records from the north Tasman and Coral Seas, there is no knowledge of the relative abundance of Harrisson’s Dogfish outside Australian waters. There is limited commercial fishing activity across these areas.

Assuming that the main population of Harrisson’s Dogfish is off eastern Australia (including adjacent seamounts and Lord Howe Island), it is likely that there is still some low-level fishing mortality, in both the lightly-fished northern part of its range and the severely depleted southern part of its range, possibly resulting in a continuing slow decrease in the total population.

Graham and Daley (2011) discuss in detail the depth distribution, biology and stock structure of Harrisson’s Dogfish off southeastern Australia. The species inhabits the upper- to mid-continental slope, mainly in depths between 350 and 800 m but with an overall depth range of 275–1,050 m. Although the diet of this species consists mainly of mesopelagic teleost fishes (particularly myctophids), cephalopods and crustaceans, Harrisson’s Dogfish appears to be essentially demersal in habit and is highly vulnerable to demersal trawling and longlining. Maximum size is 112 cm total length (TL), with females mature at ~99 cm TL and males at ~84 cm TL; size at birth is ~35 cm TL (Graham and Daley 2011). It has a very low fecundity of one to two pups every two (or possibly three) years, high longevity (closely related species live for at least 46 years according to preliminary ageing studies by Fenton (2001)) and an estimated age at first maturity (>23 years (Whitely 2004)). Taking these attributes into account, Forrest and Walters (2009) estimated that the annual Maximum Sustainable Yield (MSY) of Gulper Sharks from southeastern Australian waters was in the order of 1%, indicating that any recovery of over-fished stocks would be very slow.

From the inception of the upper slope trawl fishery off southeastern Australia in the 1970s, gulper sharks (including Harrisson’s Dogfish) were harvested for human consumption but numbers on the trawl grounds off NSW were quickly reduced to extremely low levels (Graham et al. 2001). In the 1980s and 1990s, gulper sharks were also targeted by deepwater gillnets and lines in a number of localities off southern Australia for their meat and livers (Daley et al. 2002). Since the year 2000, small quantities of gulper sharks, including Harrisson’s Dogfish, continued to be taken as bycatch from Australian waters with annual landings since 2002 totalling less than 10 tonnes (Wilson et al. 2009).

however, from February 2013 it became illegal to retain any Harrison's Dogfish caught by commercial (and recreational) fisheries off eastern Australia (AFMA 2012b, NSWDPI 2013).

Commercial fishing activities constitute the main threat to Harrisson’s Dogfish because the core depth of the species (350–800 m) largely coincides with the most heavily fished depths by trawlers and longliners operating on the upper slope around southeastern Australia. In the period 1975–2000, the population south of Newcastle (central NSW) was severely impacted by trawling and targeted gillnetting and its relative abundance was reduced to <5% of historical levels (Graham et al. 2001, Daley et al. 2002, Wilson et al. 2009). Commercial fishing continues to impact on the remaining stock with up to five trawlers operating seasonally in the deepwater sector of the NSW Offshore Trawl Fishery between Newcastle (33°00’S) and Sydney (33°40’S) while south from Sydney about 30 trawlers and three auto longliners regularly operate in upper slope depths in the Commonwealth Trawl and Scalefish Hook Sectors of the Southern and Eastern Scalefish and Shark Fishery (SESSF). In 2010, The stock status for the three species of upper slope gulper sharks (Harrisson’s Dogfish, Endeavour Dogfish C. moluccensis and Southern Dogfish C. zeehaani) on southeastern Australian grounds was assessed as ‘overfished’ and ‘subject to overfishing’ (Stobutzki et al. 2011).

On the coast and adjacent seamounts off Queensland and northern NSW, small-scale line fishing (drop-line and minor-line) is believed to have minimal impact on Harrisson’s Dogfish. However, automatic longlining on seamounts in the Australian zone of the Coral and Tasman Seas (permissible under Australian Government permits) poses a greater potential threat to Harrisson’s Dogfish populations although the very steep terrain and high capture rates of (unwanted) spurdogs (Squalus spp.) make fishing by this method less likely at these locations (K. Graham pers. obs.).

North of New Zealand, a trawl fishery operates on the West Norfolk Ridge, and drop-lining for large teleosts occurs on the Three Kings Rise, West Norfolk Ridge and Wanganella Bank but, with only two records of Harrisson’s Dogfish from this region, it is unknown if these fishing activities have any impact on gulper shark populations, and there is no information on any gulper shark bycatch from any of these fishing activities (C. Duffy pers. comm. 2010). Because of its steep rocky topography, there is almost no trawling and very little longlining on the Kermadec Ridge.

In 2002, the Australian Fishery Management Authority (AFMA) introduced trip limits for commercial vessels operating in the Southern and Eastern Scalefish and Shark Fishery (SESSF) of 150 kg (carcass weight) of gulper sharks including a maximum of 30 kg of Harrisson’s Dogfish. This was further reduced to a combined total of 15 kg per day (90 kg per trip for trips >6 days) for Harrisson’s Dogfish, Endeavour Dogfish, Southern Dogfish and Greeneye Spurdog (Squalus chloroculus) with a combined annual catch limited to 4.5 tonnes (AFMA 2010a). In NSW, similar complementary landing restrictions have also been legislated.

Spatial management measures designed to protect gulper sharks were introduced by AFMA in 2007 with the closure of small areas on the upper slope off Sydney (for Endeavour Dogfish) and eastern Bass Strait (for Harrisson’s Dogfish) to trawl and hook methods; two additional closures off eastern Bass Strait were implemented in December 2010 (AFMA 2010b). In addition, the closure of almost all ground deeper than 700 m south of Sydney (Orange Roughy Conservation Programme) also affords some protection to Harrisson’s Dogfish in the deeper part of its depth range (see Stobutzki et al. 2011). As part of AFMA’s upper-slope dogfish management strategy for the SESSF, all waters deeper than 183 m have been closed to shark-hook and gillnet methods, and the Barcoo and Taupo Seamounts have been closed to all fishing (AFMA 2010b).

In October 2012, a revised Upper-slope Dogfish Management Strategy was released by AFMA and included actions designed to rebuild the Harrisson’s Dogfish population (AFMA 2012b). The revised strategy ‘relies on a new network of spatial closures supplemented by a range of operational measures including regulated handling practices, 100% monitoring, move-on provisions and no retention of gulper sharks’. New provisions include increasing the areas of the Sydney and Eastern Bass Strait (Flinders Research Zone and Harrisson’s Dogfish Closure) closures, effective to all methods of fishing. Management of the Tasmantid Seamounts off NSW and Queensland have also been changed: the Derwent Hunter Seamount is now closed to all fishing while the Britannia and Queensland Seamounts are closed to demersal longlining with fishing restricted to handlines with powered reels. The Barcoo and Taupo Seamounts remain closed to trawling but open to line fishing. All seamount fishing is ‘subject to regulated handling practices and 100% monitoring’; there will also be a ‘vessel interaction limit of three gulper sharks and if reached the closure area will be closed to that boat for 12 months’. In addition, the taking of Harrison's Dogfish for sale is prohibited across the whole SESSF. Similarly, in February 2013, the NSW Government gazetted a regulation prohibiting the taking of Harrison's Dogfish in waters under its jurisdiction (NSWDPI 2013).

Harrisson’s Dogfish has also been nominated for listing as a threatened species under Australia’s Environment Protection and Biodiversity Conservation Act 1999, with a decision pending.

North of New Zealand where Harrisson’s Dogfish has been recorded, both the Kermadec and Colville Ridges are covered by large benthic protection areas (BPAs) (C. Duffy pers. comm. 2010).